PARIS -- The European spacecraft Mars Express is to make a daring flyby of the Martian moon Phobos in the hope of gaining insights into its enigmatic surface, temperature and geological past, the European Space Agency (ESA) said on Wednesday.

On July 23, the unmanned craft will swoop to within just 97 kilometers (60 miles) of Phobos, using a battery of instruments, including a high-resolution stereo camera, infra-red scanner and atmospheric spectrometer.

A program of five flybys have been scheduled by Mars Express. The first, on July 12, took place at an altitude of 563 kilometers (351 miles).

The second, on Thursday July 17, entails an altitude of 273 kms (170 miles). The two others, on July 28 and on August 3, will have a closest approach of 361 and 664 kms (225 and 415 miles) respectively.

Mars has two small satellites, Phobos and Deimos, named after the horses Fear and Panic that hauled the chariot of Ares, the Greek god of war.

The moons are irregularly shaped, measuring respectively just 26 kms (16.25 miles) and 16 kms (10 miles) across at their widest.

They were discovered in 1870, but little is known about them, and some astronomers believe they are wandering asteroids that became ensnared by Mars' gravity and never left its orbit.

Russia is to send a lander, called Phobos-Grunt, to Phobos in 2009, and the flybys hope to capture an image of the intended landing site for the mission. The "Grunt" refers to samples of soil which the mission hopes to return to Earth for analysis.

Mars Express was launched in 2003.